The present invention relates to an articulation intended particularly for a motor vehicle seat.
The state of the art already knows an articulation of the type with parallel gears comprising two coaxial annulus gears with internal sets of teeth of different pitch, one stationary and the other mobile, meshing with at least one planet bearing two external sets of teeth that mate with the internal sets of teeth and are off-centred with respect to these internal sets of teeth, the axis of the articulation coinciding with the axis of the annulus gears.
An articulation of this type is advantageously used in a motor vehicle seat to connect the seat cushion and the backrest of the seat together. The stationary and mobile annulus gears are, respectively, as one with the seat cushion and with the backrest. The articulation allows the inclination of the backrest with respect to the seat cushion to be adjusted continuously.
Customarily, the articulation is operated by an operating knob which the user turns in the desired direction in order to adjust the inclination of the backrest. The articulation allows very accurate infinitesimal continuous adjustment of the inclination of the backrest, without the user having to exert a significant amount of torque on the operating knob because of the high degree of demultiplication obtained by the gearing of the articulation.
However, when the user wishes to move the backrest through a large angle, for example to bring it from a normal, roughly vertical position into a reclined, roughly horizontal position, he or she has to turn the operating knob through a great many turns, which is a lengthy and irksome operation.